# What is CPI (cost per install)?

> CPI is what you pay in ads for each app install. Formula, a worked example in rupees, and why install cost alone can hide poor-quality users.
- **Author**: Marxx
- **Published**: 2026-11-15
- **Category**: Metrics
- **URL**: https://marxx.ai/library-glossary/cpi

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CPI (cost per install) is what you pay in ads for each time someone installs your app. If INR 1,00,000 of ads brings 4,000 installs, your CPI is INR 25. Here, CPI means cost per install.

## The formula

CPI = ad spend / installs

On Meta, installs come under the App promotion objective. Meta describes it as a way to get people on mobile devices to install or take a specific action in your app ([Meta Help Center](https://www.facebook.com/business/help/1438417719786914), checked 2026-10-20).

## A worked example

Say you spend INR 1,00,000 on an app install campaign. The numbers are made up.

| Step | People | Cost for each |
|---|---|---|
| Installs | 4,000 | **INR 25** (CPI) |
| Sign up | 1,000 | INR 100 |
| First order | 250 | INR 400 |

- CPI = 1,00,000 / 4,000 = INR 25
- Cost per sign-up = 1,00,000 / 1,000 = INR 100
- Cost per first order = 1,00,000 / 250 = INR 400

An install is only the first step. A cheap CPI is no use if few installers ever sign up or buy.

## Why a low CPI can mislead you

Say channel A gives you installs at INR 15 and channel B at INR 40. In channel A, 2 in 100 installers place an order. In channel B, 8 in 100 do.

- Channel A: cost per order = 15 / 0.02 = **INR 750**
- Channel B: cost per order = 40 / 0.08 = **INR 500**

The channel with the dearer install is the cheaper way to get an order.

## How to use CPI

1. Track CPI by campaign and creative, but do not stop at CPI.
2. Pair it with a deeper event: sign-up, first purchase or first deposit. That is a [CPA](/glossary/cpa).
3. Compare the cost of a customer with what that customer is worth over time. See the [LTV to CAC ratio](/glossary/ltv-to-cac-ratio).
4. Test hooks that show the app in use. See [hooks for app ads](/templates/hooks-for-app-ads) and [app install ad copy examples](/templates/app-install-ad-copy-examples).

## FAQ

### What is a good CPI?

It depends on your country, category and the value of a user. Compare your CPI to what an installer earns you, not to another app's number.

### Is CPI the same as CPA?

CPI is a type of CPA, where the action is an install. CPA can also mean a purchase or a sign-up.

### How do I lower CPI?

Test new creative, show the app screen early and widen your audience. Then check that the installs still reach your key event.

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